JPH10224044A - Multilayer board for mounting filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent signal suppression level from degrading on the outside of the band of a filter while minimizing the layout space. SOLUTION: The board for mounting an SAW(surface acoustic wave) filter comprises a multilayer board 2 having a first layer on which first and second ground patterns G1, G2 to be connected, separately, with the input side ground 21 and the output side ground 20 of an SAW filter 2 are formed. The multilayer board 2 has a second layer on which a third ground pattern G3 provided with a punched part G3H at a position between through holes T1, T2 and connected with the first and second ground patterns G1, G2 on the first layer through the through holes T1, T2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter-mounted multilayer board, and more particularly, to a filter-mounted multilayer board having a long conduction path between the first port side and the second port side of the filter.

[0002]

2. Description of the Related Art For example, in a base station radio apparatus for mobile communication, a radio apparatus for mobile station, etc., many RF bands, IF band filters and base band filters are used for the purpose of interference elimination and channel selection. I have. Filters are classified into dielectric filters, SAW filters, LC filters, crystal filters, piezoelectric ceramic filters, digital filters, and the like according to active principles and structures. For these various filters, optimal filters are selected according to the required electrical performance and size.

The above-mentioned SAW filter is an abbreviation of a surface acoustic filter, and is a filter utilizing mechanical vibration propagating on the surface of a piezoelectric substrate. In the SAW filter, when an AC signal is applied to the input electrode, a surface acoustic wave is generated by the piezoelectric effect and propagates to the output electrode. The SAW filter uses the frequency characteristics of the conversion of the electric / surface acoustic waves of the electrodes as the amplitude characteristics of the filter, and uses the phase characteristics when the surface acoustic waves propagate between the input and output electrodes as the phase characteristics of the filter. is there.

The SAW filter is made of quartz, LiNb
Crossed electrode pairs are formed on a piezoelectric substrate such as O3 or ZnO by photolithography or the like, and these are used as input / output electrodes. The electrode pitch is equal to the wavelength of the oscillating surface acoustic wave.
The wavelength of a surface acoustic wave is about five orders of magnitude smaller than that of an electromagnetic wave. Therefore, SAW filters are smaller and smaller than dielectric filters.
Lightweight. Also, since it can be manufactured by the same photolithography as LSI manufacturing, it is suitable for mass production and no adjustment.

Such a SAW filter is used in a frequency band ranging from several + MHz to a quasi-microwave band, and has applications such as a first IF filter, an antenna duplexer, and an interstage filter. In the RF band, the surface acoustic wave has a wavelength of about 1 μm at 1 GHz, so that extremely fine processing technology is required to form an electrode. In addition to the development of this ultra-fine processing technology, the practical use of high sound speed and low propagation loss substrates
The frequency of the AW filter has been increased, and it has been used as an RF filter for PDC 1.5 GHz.

Further, the SAW filter is used as a band-pass filter for the purpose of band limitation or the like. In this case, the characteristics of the SAW filter within the band are important. Out-of-band signal suppression levels become important. The signal suppression level outside this band may be deteriorated depending on how the ground is taken.

By the way, in mobile communication equipment and the like,
The wireless circuit portion is often formed on a multilayer substrate. FIG.
3 is a schematic sectional view showing a schematic structure of a conventional SAW filter-mounted multilayer substrate.

As shown in FIG. 2, the multilayer board 3 is composed of an insulating layer 3A and four conductive layers, and the SAW filter 2 is mounted on the first layer of the multilayer board 3. S
Grounds 2I, 2 on the input and output sides of AW filter 2
O is directly connected to the ground pattern G1 arranged on the first layer by soldering or the like. In such a structure, as shown by an arrow line P in FIG.
And the path of the conduction path between the output ground 20 and the input ground 21 and the output ground 20 are shortened.
In some cases, isolation (insulation) of the SAW filter 5 cannot be completely achieved, which is one of the causes of deteriorating the signal suppression level outside the band of the SAW filter 5.

In the prior art shown in FIG. 3, similarly to FIG. 2, the multilayer substrate 3 is composed of an insulating layer 3A and four conductive layers, and the SAW filter 2 is composed of the multilayer substrate 3
Is mounted on the first layer. The first layer of the multilayer substrate 3 includes:
A pair of first and second ground patterns G separated from each other
1 and G2 are arranged on the input side and the output side of the SAW filter 2, respectively. The second layer includes the SAW filter 2 and the first and second ground patterns G1 and G disposed on the first layer.
Third ground pattern G3 having an area larger than 2
Is arranged. In the first and second layers, the input side ground 2I and the output side ground 20 of the SAW filter 2 are provided.
, The first ground pattern G1 and the second ground pattern G2 and the third ground pattern
Through holes (through holes) T1 and T2 for conducting the ground pattern G3 are formed.

The path of the conduction path between the input-side ground 2I and the output-side ground 2O of the SAW filter 2 extends from the input-side ground 2I to the first ground pattern G as indicated by an arrow P.
1 and through the through hole T1, through the third ground pattern G3, and through the through hole T2 and the second ground pattern G2 to the second output side ground 5B.

Generally, in a multilayer substrate, the interlayer distance is often small, and in such a structure, as described above, the path of the conduction path between the input-side ground 2I and the output-side ground 2O is shortened. Similarly to the structure, isolation (insulation) between the input-side ground 2I and the output-side ground 2O may not be completely achieved, which is one of the causes of deteriorating the signal suppression level outside the band of the SAW filter.

Therefore, conventionally, in order to lengthen the path of the conduction path between the input side ground and the output side ground, FIG.
There has been proposed a SAW filter-mounted multilayer substrate such as that described above.
FIG. 4 is a diagram showing a schematic configuration of a conventional SAW filter-mounted multilayer substrate, and FIG. 4A is a schematic plan view thereof (the insulating layers 3A, 3 and 4 are omitted in FIG. 4). .),
FIG. 4B is a cross-sectional view taken along the line AA in FIG.

As shown in FIG. 1, the basic structure of the multilayer substrate 1 on which a SAW filter is mounted is a multilayer substrate 3 in which four conductive layers are arranged on an insulating layer 3 A, and a first substrate formed on the multilayer substrate 3. And a SAW filter 2 mounted on the layer.

More specifically, a pair of ground patterns 1A and 1B which are electrically separated from each other are formed on the first layer.
A third third ground having a larger area than the SAW filter 2 and the first ground patterns G1 and G2 disposed on the second layer is provided on the input side and the output side of the filter 2. The pattern G3 is formed. Then, the first layer and the second layer of the multilayer substrate 3 are located at positions separated from the input-side ground 2I and the output-side ground 20 of the SAW filter 2 by a distance larger than the separation distance t shown in FIG. Through holes (through holes) T1 and T2 for conducting the ground pattern G1, the second ground pattern G2, and the third ground pattern G3 are formed.

According to this structure, since the distance between the input side ground 2I and the output side ground 20 of the SAW filter 2 and the through holes T1 and T2 is large, the input side ground and the output side ground are indicated by the arrow P in FIG. The path of the conduction path between the ground 2I and the output-side ground 2O becomes longer, so that the insulation between them can be improved, and the signal suppression level outside the band of the SAW filter 2 can be improved.

[0016]

However, in the configuration shown in FIG. 4, the SAW filter 2 and the through-hole T
1, the distance between the input side ground and the output side ground 5B of the SAW filter 2 is increased by increasing the distance between the input side ground and the output side ground 5B to improve the insulation between the input side and the output side. There is a problem that the area required for the layout around the SAW filter becomes large, which in turn reduces the degree of freedom of layout and hinders high-density mounting.
The present invention has been made in view of the above problems, and has as its object to improve a signal suppression level outside a filter band while minimizing a layout space.

[0017]

According to a first aspect of the present invention, there is provided a filter mounting structure in which a filter is mounted on a multi-layer substrate, wherein the filter is mounted on a layer of the multi-layer substrate on which the filter is mounted. A first ground pattern and a second ground pattern which are electrically connected to the first port side and the second port side of the filter, respectively, and are separated from each other, form a conduction path between the first port side and the second port side. In order to lengthen the path, the first ground pattern and the second ground pattern are electrically connected to other layers of the multilayer substrate via at least one pair of through holes, respectively, and are sandwiched between the at least one pair of through holes. The above problem is solved by forming a third ground pattern having a punched portion at a position.

That is, according to the first aspect of the present invention, in the filter mounting multilayer board in which the filter is mounted on the multilayer board, the first port side and the second port side of the filter are electrically connected to the filter mounting layer, respectively. To form a first ground pattern and a second ground pattern that are separated from each other, and to increase the length of the conduction path between the first port side and the second port side, to another layer of the multilayer substrate, A third ground pattern electrically connected to the first ground pattern and the second ground pattern via at least one pair of through holes, and having a punched portion at a position sandwiched between the at least one pair of through holes, was formed.

Therefore, in order to lengthen the path of the conduction path between the first port side and the second port side of the filter, the filter is provided with a ground pattern having a punched portion. Even when the distance is small, it is possible to lengthen the path of the conduction path between the first port side and the second port side, and to minimize the layout space while keeping the layout space between the first port side and the second port side. Isolation can be achieved, and the signal suppression level outside the band can be improved.

According to a second aspect of the present invention, there is provided a filter mounting multilayer board in which a filter is mounted on a multilayer board, wherein an input side of the filter is provided on a first layer of the multilayer board on which the filter is mounted. The first and second ground patterns are electrically connected to a ground and an output ground, respectively, and are electrically separated from each other. In order to lengthen a path of a conduction path between the input ground and the output ground, The second layer of the multilayer substrate is electrically connected to the first ground pattern and the second ground pattern via at least a pair of through holes, respectively, and has a punched portion at a position sandwiched between the at least one pair of through holes. The above problem is solved by forming three ground patterns.

That is, according to the filter mounting multilayer substrate of the present invention, in the filter mounting multilayer substrate in which the filter is mounted on the multilayer substrate, the input side ground of the filter is provided on the first layer of the multilayer substrate on which the filter is mounted. In order to form first and second ground patterns that are electrically connected to each other and are separated from each other, and that a path of a conduction path between the input side ground and the output side ground is lengthened,
The second layer of the multilayer substrate is electrically connected to the first ground pattern and the second ground pattern via at least a pair of through holes, respectively, and has a punched portion at a position sandwiched between the at least one pair of through holes. 3 Form a ground pattern.

Accordingly, since the filter is provided with a ground pattern having a punched portion in order to lengthen the path of the conduction path between the input side ground and the output side ground of the filter, the distance between the filter and the through hole is reduced. In this case, the length of the conduction path between the input side ground and the output side ground can be lengthened, and the input side ground and the output side ground can be isolated while minimizing the layout space. It is possible to improve the signal suppression level outside the band.

In this case, the filter may be a SAW, such as a filter-mounted multilayer board according to the invention of claim 3.
It may be a filter.

Therefore, when the SAW filter is mounted on a multilayer substrate, it is possible to improve the signal suppression level outside the band.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a filter-mounted multilayer substrate according to the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of a SAW filter-mounted multilayer substrate according to the present invention, and FIG. 1A is a schematic plan view thereof (the insulating layer 3A, 3 layers, and 4 layers in FIG. 1B is omitted from the drawing), and FIG.
The sectional views in the A section are shown respectively. In this figure, parts having the same functions as those in FIGS. 2 to 4 are denoted by the same reference numerals.

As shown in the figure, the basic configuration of the SAW filter-mounted multilayer substrate 1 includes a multilayer substrate 3 in which four conductive layers are arranged on an insulating layer 3A, and a first substrate formed on the multilayer substrate 3.
And a SAW filter 2 mounted on the layer.

More specifically, as shown in FIG. 1, the multi-layer substrate 3 is formed of a four-layer substrate, and a pair of input and output electrode patterns C1 and C2 are formed on the first layer 1 in a reverse symmetry. And a pair of first and second ground patterns G1 and G2 separated from each other at positions that are oppositely symmetric with respect to the pair of input and output electrode patterns C1 and C2.

The second layer is provided with a third ground pattern G3 having a rectangular punched portion G3H at a substantially central portion. The first and second ground patterns G3 provided on the first layer are provided.
1, G2 and a third ground pattern G3 disposed in the second layer
Through holes (through holes) T1 and T2 for conducting the
Are punched portions G3H of the third ground pattern G3.
Is formed at a position sandwiching. As shown in FIG. 1B, the third and fourth layers have wiring patterns C3.
Is arranged.

The above-described SAW filter 2 has, for example, L
Cross electrode pairs (not shown) are formed on a piezoelectric substrate such as iNbO 3 by photolithography or the like, and each of these cross electrode pairs becomes an input electrode and an output electrode. This S
The AW filter 2 is mounted over a pair of first and second ground patterns G1 and G2 formed on the first layer,
The input terminal 2C and the output terminal 2D are connected to the input electrode pattern C1 and the output electrode pattern C2 by soldering, respectively. The input side ground 2I of the SAW filter 2 is connected to the first ground pattern G1. The side grounds 20 are respectively connected to the second ground patterns G2 by soldering or the like.

In the SAW filter-mounted multilayer substrate 1 having the above configuration, as shown by the arrow P in FIG.
Input ground 2I and output ground 2 of W filter 2
The path of the conduction path to O passes from the input-side ground 2I through the first ground pattern G1 of the first layer and the through hole T1, and the punched portion G of the third ground pattern G3 of the second layer.
Following the shortest path bypassing 3H, it reaches the output side ground 20 via the through hole T2 and the second ground pattern G2 of the first layer.

Therefore, the third ground pattern G of the second layer
Because the punched portion G3H is formed in the SAW filter 3, the length of the conduction path between the input-side ground 2I and the output-side ground 20 of the SAW filter 2 can be made longer than in a configuration in which the punched portion G3H is not formed. It is possible to improve the insulation between input and output. In addition, unlike the related art shown in FIG. 3, the length of the conduction path between the input and output grounds can be increased without increasing the distance between the SAW filter and the through hole, and the distance between the input and output grounds can be increased. Can be improved in insulation. In other words,
The path of the conduction path between the input and output of the SAW filter can be lengthened while minimizing the layout space, isolation between the two can be achieved, and the signal suppression level outside the band can be improved.

As described above, the SA of this embodiment
The W filter mounting multilayer substrate 1 is formed on the first layer of the multilayer substrate 3,
First and second ground patterns G1 and G2 separated from each other and connected to the input side ground 2I and the output side ground 2O of the SAW filter 2, respectively, are formed on the second layer.
First and second ground patterns G1, G2 of the first layer
And the third ground pattern G3 having a punched portion G3H formed at a position sandwiched between the through holes T1 and T2. Even when the distance between T1 and T2 is small, it is possible to lengthen the path of the conduction path between the input and output grounds, and to isolate the input and output while minimizing the layout space. It is possible to improve the signal suppression level outside the band.

In addition, even in the case where it is found that the isolation is not obtained after trial production on a substrate on which layout has been completed in advance, a punched portion is formed in the ground pattern as in this embodiment. If the pattern is changed, it is possible to take measures to improve the characteristics (signal suppression level) without requiring a significant layout change and pattern examination.

In the above embodiment, an example is shown in which a SAW filter is mounted. However, the present invention is not limited to this, and can be applied to other filters.

Further, in the above embodiment, the SAW filter is mounted on the first layer of the multilayer substrate 3 and the ground pattern having the punched portion is formed on the second layer. The ground pattern having the punched portion is not limited to three layers or four layers.
It may be configured to be formed in a layer.

In the above-described embodiment, the punched portion of the ground pattern is rectangular. However, the shape of the punched portion is not limited to this. If possible,
Any shape may be used.

[0038]

According to the first aspect of the present invention, in order to lengthen the path of the conduction path between the first port side and the second port side of the filter, the filter is provided with a ground pattern having a punched portion. Therefore, even when the distance between the filter and the through-hole is small, it is possible to lengthen the path of the conduction path between the first port side and the second port side, and to reduce the layout space while minimizing the layout space. 1 port side and 2nd
Isolation from the port side can be achieved, and the signal suppression level outside the band can be improved.

According to the second aspect of the present invention, the filter is provided with a ground pattern having a punched portion in order to lengthen the path of the conduction path between the input side ground and the output side ground of the filter. Even when the distance to the hole is small, it is possible to lengthen the path of the conduction path between the input side ground and the output side ground, and to minimize the layout space while maintaining the layout between the input side ground and the output side ground. And the signal suppression level outside the band can be improved.

According to the third aspect of the invention, when a SAW filter is mounted on a multilayer substrate, it is possible to improve the signal suppression level outside the band.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a multilayer substrate mounted with a SAW filter according to the present invention, and FIG.
FIG. 2B is a cross-sectional view taken along the line AA in FIG.

FIG. 2 is a schematic sectional view showing a schematic structure of a conventional SAW filter-mounted multilayer substrate.

FIG. 3 is a schematic sectional view showing a schematic structure of a conventional SAW filter-mounted multilayer substrate.

FIG. 4 is a diagram showing a schematic configuration of a conventional SAW filter-mounted multilayer substrate, and FIG. 4 (A) is a schematic plan view thereof;
FIG. 4B is a cross-sectional view taken along the line AA in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multilayer board mounting SAW filter 2 SAW filter 2I Input side ground 2O Output side ground 2C Input terminal 2D Output terminal 3 Multilayer substrate G1 First ground pattern G2 Second ground pattern G3 Third ground pattern G3H Punching part C1 Input electrode pattern C2 Output Electrode pattern C3 Wiring pattern 3A Insulation layer

Claims (3)

[Claims] 1. A filter mounting multilayer board in which a filter is mounted on a multilayer board, wherein the filter is mounted on a layer of the multilayer board and electrically connected to a first port side and a second port side of the filter, respectively. A first ground pattern and a second ground pattern separated from each other;
A ground pattern is formed, and at least one of the first ground pattern and the second ground pattern is formed on another layer of the multilayer board so as to lengthen a path of a conduction path between the first port side and the second port side. A filter mounting multilayer substrate, wherein a third ground pattern electrically connected through a pair of through holes and having a punched portion at a position sandwiched between the at least one pair of through holes is formed. 2. A filter mounting multilayer board in which a filter is mounted on a multilayer board, wherein a first layer of the multilayer board on which the filter is mounted is electrically connected to an input ground side and an output ground side of the filter, respectively. Forming first and second ground patterns separated from each other, and extending the first ground pattern on a second layer of the multilayer substrate so as to lengthen a path of a conduction path between the input-side ground side and the output-side ground side. A third ground pattern electrically connected to the pattern and the second ground pattern via at least one pair of through holes, and having a punched portion at a position sandwiched between the at least one pair of through holes; Mounting multilayer board. 3. The filter-mounted multilayer substrate according to claim 1, wherein said filter is a SAW filter.